1. Field of the Invention
The invention relates to a control assembly particularly for a single station, single lever control of a marine power unit having a throttle and reversible gearbox controlled by the lever assembly.
2. Prior Art
Single lever control assemblies for controlling concurrently with one manual lever a throttle and a reversible gearbox and clutch assembly of a marine power unit are old. Essentially, the control assembly permits an operator to control a marine power unit from idle to full throttle in either the forward or reverse modes using only a single lever. In some applications, it is also desirable to provide a manual override throttle for actuation of the engine when the gearbox is in neutral, so as to operate auxiliary equipment such as winches or pumps. The normal operation of a single lever control assembly is as follows. From an initial position of the lever in neutral, with the throttle at idle, a primary movement of the lever results in engagement of the forward or reverse gears of the gearbox, without a change in throttle setting, that is the throttle remains at idle so as to prevent damage to the gearbox. When the particular gear is engaged, additional or secondary movement of the lever results in acceleration of the engine from idle to full throttle, with the clutch remaining engaged throughout the full movement.
Various devices have been developed to attain the above functions, for example see devices described in two patents of the present applicant, namely U.S. Pat. No. 3,202,011 issued in 1965 and U.S. Pat. No. 3,330,390 issued in 1967. Each of the devices of these patents performs a generally similar function, although they may have applications in control systems having more than one station, that is a control system wherein the engine and clutch can be controlled from more than one station or location having similar control levers. In each of these structures, and in all of the structures known to the inventor, there is a non-linear relationship between angular rotation of the lever following gear engagement, and acceleration of the engine. That is there is not a simple direct proportional relationship between the rotation of the lever controlling engine rpm following engagement of the gears. This presents difficulties for accurate control of the vessel, and at extreme ends of the range, it can be difficult to select the desired engine rpm. Furthermore, many of the devices are relatively complex with many moving parts, some of which must be accurately manufactured and maintained and this increases the cost of purchasing and servicing such devices. Furthermore, the provision of a manual override control for the throttle for powering auxiliary equipment also increases complexity and, in some instances, there is a possibility of damage to the engine due to the omission or malfunction of an interlock means that could result in engagement of the gearbox when the engine is at a speed other than idle.